The FBI has searched a mail facility in Florida, as investigators try to find out who is behind a series of crude explosive packages targeting several prominent Democrats.
Devices have been sent to eight high-profile people, including ex-President Barack Obama and actor Robert De Niro.
US officials say some of the packages appear to have been sent from a postal centre in north-western Miami.
The FBI has not yet released any details of their investigation.
Similar packages have also been sent to former Vice-President Joe Biden and former Secretary of State Hillary Clinton, among others.
The postal facility searched is in Opa-locka, where security footage was being scrutinised. A bomb squad and canine unit accompanied federal officials, police from Miami-Dade County said.